I don't agree that LSU and aTm are the only two good offenses we've faced this season. Ole Miss and TN both have good offenses and horrible defenses. Michigan and MSU have decent offenses as well.
I personally think LSU caught lightening in a bottle and there wasn't a whole lot we could do. aTm, on the other hand, is a different story. Our defenses throughout the Saban era have struggled against up-tempo, spread offenses that employ really good dual-threat QBs. Yesterday, our defense (for whatever reason) was clearly not ready at the start of the game. Injuries, LSU hangover, impromper preparation, whatever, their offense took a page right out of the Utah 2009 Sugar Bowl playbook and kept our defense on their heels for the entire first quarter. By the time the coaches got them settled down and made adjustments, the damage was done.
I've been amazed the last two weeks at the amount of arm-tackling by our defense (and not wrapping up and finishing plays), which usually is a sign of fatigue or just a basic lack of speed and quickness. I agree with the thought that this type of offense is here to stay and our staff has got to figure out how scheme against it better. I'm also concerned that - for all of the hype over our recruiting classes, we don't have the players on defense who can hang against this type of offense. That, or their just not in good enough shape to play at that speed.